Repair of a composite sandwich structure having a perforated skin

Abstract

A method of restoring a section of a composite having a honeycomb bonded to a perforated skin includes the steps of separating a first honeycomb from the perforated skin to expose a portion of the perforated skin, inserting pins through perforations in the perforated skin, extending the pins through a repair material, attaching the repair material to the exposed portion of the perforated skin, and attaching a second honeycomb to the repair material. The method may include removing material from the exposed portion of the perforated skin, prior to inserting pins through the perforations, to create a more even bonding surface for attaching the repair material.

1 . A method of restoring a section of a composite having a honeycomb bonded to a perforated skin, the method comprising:
 separating a first honeycomb from the perforated skin to expose a portion of the perforated skin;   inserting pins through perforations in the perforated skin;   extending the pins through a repair material;   attaching the repair material to the exposed portion of the perforated skin; and   attaching a second honeycomb to the repair material.   
   
   
       2 . The method of  claim 1  further comprising:
 removing the pins from the perforations in the perforated skin.   
   
   
       3 . The method of  claim 1  further comprising:
 positioning the pins in a retaining device prior to inserting the pins through the perforations in the perforated skin.   
   
   
       4 . The method of  claim 1  further comprising:
 removing material from the exposed portion of the perforated skin to create an even bonding surface prior to inserting the pins through the perforations in the perforated skin.   
   
   
       5 . The method of  claim 1  further comprising:
 applying an adhesive to an exposed portion of the perforated skin prior to inserting pins through perforations in the perforated skin.   
   
   
       6 . The method of  claim 5  wherein the adhesive is a paste epoxy. 
   
   
       7 . The method of  claim 1  wherein the repair material includes at least one leveling ply. 
   
   
       8 . The method of  claim 7  wherein the leveling ply is fiberglass. 
   
   
       9 . The method of  claim 1  wherein attaching the repair material to the exposed portion of the perforated skin includes bonding a first adhesive layer to the perforated skin and bonding the repair material to the first adhesive layer. 
   
   
       10 . The method of  claim 9  wherein attaching a second honeycomb to the repair material includes bonding a second adhesive layer to the repair material and bonding the second honeycomb to the second adhesive layer. 
   
   
       11 . The method of  claim 10  wherein the repair material, the first adhesive layer and the second adhesive layer each include an epoxy resin. 
   
   
       12 . The method of  claim 1  wherein the composite includes a solid skin and the honeycomb is sandwiched between the solid skin and the perforated skin. 
   
   
       13 . The method of  claim 12  further comprising:
 removing a first section of the solid skin from the composite prior to separating the first honeycomb from the perforated skin.   
   
   
       14 . The method of  claim 13  further comprising:
 attaching a replacement section of solid skin to the composite to cover the second honeycomb.   
   
   
       15 . The method of  claim 14  further comprising:
 attaching at least one ply to the solid skin to cover the replacement section of solid skin.   
   
   
       16 . A composite having a section restored by the method of  claim 1 . 
   
   
       17 . The composite of  claim 16  wherein the composite is a part in an aircraft engine. 
   
   
       18 . The composite of  claim 16  wherein the composite is an acoustic liner of a gas turbine engine. 
   
   
       19 . A method of restoring a section of a composite having a perforated skin, a solid skin and a honeycomb between the perforated skin and the solid skin, the method comprising:
 (a) removing an undesirable section of the honeycomb and a corresponding section of the solid skin from the perforated skin, wherein an exposed portion of the perforated skin includes an uneven surface;   (b) removing at least a portion of the uneven surface to form a bonding surface on the exposed portion of the perforated skin;   (c) inserting pins into openings in the perforated skin;   (d) bonding a repair material to the exposed portion of the perforated skin, wherein the pins are extended through the repair material;   (e) bonding a replacement honeycomb to the repair material;   (f) bonding a replacement solid skin to the replacement honeycomb; and   (g) removing the pins from the openings in the perforated skin.   
   
   
       20 . The method of  claim 19  wherein removing a section of the solid skin in step (a) includes tapering a remaining portion of the solid skin around the undesirable section of the honeycomb. 
   
   
       21 . The method of  claim 19  wherein the uneven surface of the perforated skin includes compressed sections and uncompressed sections, and removing a portion of the uneven surface in step (b) includes removing at least a portion of the uncompressed sections. 
   
   
       22 . The method of  claim 19  further comprising:
 positioning the pins in a retaining device prior to inserting the pins into the openings in the perforated skin in step (c).   
   
   
       23 . The method of  claim 19  wherein the repair material is formed from at least one ply of fiberglass. 
   
   
       24 . The method of  claim 19  wherein bonding a repair material on the exposed portion of the perforated skin further comprises:
 attaching a first adhesive layer to the exposed portion of the perforated skin;   bonding the repair material to the first adhesive layer; and   bonding a second adhesive layer to the repair material.   
   
   
       25 . The method of  claim 24  wherein the pins are extended through the first adhesive layer and the second adhesive layer. 
   
   
       26 . The method of  claim 24  wherein the first adhesive layer is attached to the exposed portion of the perforated skin prior to inserting the pins into the openings in the perforated skin in step (c). 
   
   
       27 . The method of  claim 19  further comprising:
 attaching an adhesive around a perimeter of the replacement honeycomb prior to step (e) to support the replacement honeycomb.   
   
   
       28 . The method of  claim 19  further comprising:
 attaching a cover material to the solid skin after step (f) to cover the replacement solid skin.   
   
   
       29 . A composite having a restored section of honeycomb, the composite comprising:
 a honeycomb having a first end and a second end;   a perforated skin bonded to a first end of the honeycomb;   a back skin bonded to a second end of the honeycomb; and   a repair section comprising:
 a plurality of removable pins located in perforations in a portion of the perforated skin; 
 at least one repair ply attached to the portion of the perforated skin, wherein the removable pins are removably extended through the at least one repair ply; 
 a replacement honeycomb having a first end attached to the at least one repair ply; and 
 a replacement back skin attached to a second end of the replacement honeycomb. 
   
   
   
       30 . The composite of  claim 29  wherein the repair section further comprises:
 an adhesive attached to a perimeter of the replacement honeycomb to support the replacement honeycomb and attach the replacement honeycomb to the honeycomb.   
   
   
       31 . The composite of  claim 29  wherein the repair section further comprises:
 a second adhesive between the second end of the replacement honeycomb and the replacement back skin.   
   
   
       32 . The composite of  claim 31  wherein the repair section further comprises:
 a film adhesive having a first side attached to the second adhesive and a second side attached to the replacement back skin.   
   
   
       33 . The composite of  claim 29  further comprising:
 a cover ply attached to the back skin to cover the replacement back skin.   
   
   
       34 . The composite of  claim 29  further comprising:
 an adhesive to bond the at least one repair ply to the portion of the perforated skin.   
   
   
       35 . The composite of  claim 34  wherein the adhesive includes at least one of an epoxy film adhesive and a paste epoxy.